The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

Earth, Planets and Space

Table 8 Model statistics of the misfit between CHAOS-7 and other field models and 30448 vector triples of ground observatory SV (annual differences of revised monthly mean) data, between 1997.5 and 2019.5

	Misfit to SV at ground observatories
	CHAOS-7		CM6		A20		MCO_SHA_2Y
	Mean	rms	Mean	rms	Mean	rms	Mean	rms
\(\text {d}B_r/\text {d}t\) (nT/year)	0.11	3.73	− 0.05	3.84	0.14	3.81	0.11	3.88
\(\text {d}B_\theta /\text {d}t\) (nT/year)	− 0.21	3.59	− 0.27	3.67	− 0.12	3.66	− 0.12	3.51
\(\text {d}B_\phi /\text {d}t\) (nT/year)	0.01	3.31	− 0.03	3.32	0.00	3.32	0.03	3.31

Mean and rms refer to Huber-weighted values in units nT/year. Similar misfits to other field models, the CM6 model (Sabaka et al. 2020), model A20 (Alken et al. 2020) and the MCO_SHA_2Y model (Ropp et al. 2020) are also reported for reference; note these did not directly use revised monthly means in their derivation. For CM6 28,986 SV vector triples between 1999.0 and 2019.0 were considered for the comparison, while for A20 and MCO_SHA_2Y 26,159 vector triples between 2001.0 and 2019.0 were considered